Optimization of gene expression in nonactivated circulating lymphocytes.

Circulating lymphocytes are important target cells for the treatment of HIV-related and autoimmune diseases and for stimulating anti-tumor immunity. To date, gene transfection of these nonactivated cells after intravenous delivery of viral or nonviral vectors remains low although these circulating cells are highly accessible. Optimized lentiviral vectors currently can transduce less than 10% of nonactivated circulating lymphocytes. Here we report transfection of up to 15% of these nonactivated cells using liposomes directed to human CCR5 displayed on the surface of helper T cells and macrophages in transgenic mice. Attachment of modified MIP-1 beta to the surface of DNA-liposome complexes increased gene delivery and expression in nonactivated circulating lymphocytes approximately sixfold. In vitro data using these complexes to transfect PM1 cells that have elevated levels of CCR5 supported our data obtained in vivo. Therefore, ligands that bind to cell surface receptors on circulating lymphocytes can be used with optimized systemic liposomes to increase transfection and gene expression in these cells without activation.